The first aim of the continuation of the project is to examine bacterial transport in non-aqueous phase liquid NAPL-contaminated saturated media, air-sparged saturated systems, and unsaturated media. We propose to use an isolate of Pseudomonas fluorescens and Alcaligenes paradoxus in the experiments. Bacterial suspensions will be injected into columns filled with glass beads. A high density NAPL, will be added by column flooding. The second aim of the investigator is to further evaluate the soil media parameters that affect bacterial transport in saturated soils and then to extend an evaluation of the parameters to unsaturated and air-sparged systems. For the saturated media during pump and treat remediation phase of the work, the investigator will use glass beds of three different mean sizes to simulate the size distribution of a natural sediment in column experiments to study bacterial transport. Next he will mix beads of different sizes to approximate a 'sandy' soil. The three fractions will then be composited and the experiment repeated. The effect of hydrophobic NAPL's and dissolved organic matter (DOM) and biosurfactants on bacterial transport will also be measured. Finally, the investigator will examine the effects of NAPL degradation by injected microorganisms, which will be compared to chemical removal by pump and treat operations under abiotic conditions. The investigator proposes to use various models to predict bacterial transport. For the unsaturated media phase of the work Dr. Logan proposes to use a mathematical prediction model of bacterial transport. Other components of this phase include a study of the effects of rhemnolipid surfactants in the unsaturated column. Lysimeter experiments apparently using lysimeters described in project C1 are planned. He plans to perform the experiments using most of the procedures developed for the column studies. Many of the variables tested will be those used in the column experiments. Dr. Logan will determine the effects of air sparging on bacterial transport to accomplish the third objective of the project. The hypothesis is that under continuous air injection convective fluid flow is set up in the direction of the air motion and should promote bacterial motion in the direction of the gas flow. He again will use laboratory columns as well as a 'sandbox'. The sandbox permits the injection of bacterial suspensions from a cylindrical sparger placed in the center of the box. Air sparging should move bacteria in the same direction as in the column but dispersion should be enhanced in the direction of the water flow. Final experiments will test bacterial transport in NAPL- contaminated media, likely in the column.